On April 26, 1954, six-year-old Randy Kerr stood first in line at his elementary school gymnasium in McLean, Virginia, sporting a crew cut and a smile. With assembly-line precision, a nurse rolled up his left sleeve, a doctor administered the injection, a clerk recorded the details, and the next child stepped into place. “I could hardly feel it,” boasted Kerr, America’s first polio pioneer. “It hurt less than a penicillin shot.”

This procedure would become nationally routine in the coming weeks as more than a million children took part in the Salk poliomyelitis vaccine trials of 1954, the largest public health experiment in American history. National attention would be riveted on the outcome, with news coverage rivaling the other big stories from that remarkable spring—the Army-McCarthy hearings, the Supreme Court’s decision in Brown v. Board of Education, and the stunning French defeat at Dien Bien Phu. Jonas Salk’s picture adorned the cover of Time magazine. A Gallup poll showed that more Americans were aware of the polio vaccine trials than knew “the full name of the President of the United States.” Never before, it appeared, had the nation been as captivated by the pursuit of a medical or scientific objective.

Such fascination was understandable: by the 1950s, polio had become America’s most dreaded infectious disease, as it fell cruelly and inescapably every summer, putting children in particular at risk. There was no prevention and no cure—no way of telling who would get it and who would be spared. Fearing that the virus spread through water, health officials closed down swimming pools and beaches. Children were told to rest and warned to stay out of crowds. Parents gave their kids a daily “polio test.” It became the crack in America’s middle-class picture window, leaving vivid reminders for all to see: wheelchairs, crutches, leg braces, iron lungs, and deformed limbs.

Ironically, the nation’s most famous polio survivor—Franklin Delano Roosevelt—had contracted the disease at age 39 in 1921. Polio, then called “infantile paralysis,” did not reach epidemic levels in the United States until the years following World War II. As president, Roosevelt had helped found the National Foundation for Infantile Paralysis, which would become the March of Dimes, a foundation devoted to helping rehabilitate polio survivors and supporting the quest for a vaccine. The organization revolutionized the way charities raised money, recruited volunteers, and penetrated the mysterious world of medical research. Among the scientists it funded were the bitter laboratory rivals Albert Sabin at the University of Cincinnati and Jonas Salk at the University of Pittsburgh. Sabin championed a live-virus oral polio vaccine (the sugar-cube method) designed to trigger a natural infection strong enough to generate lasting antibodies against polio, yet too weak to cause a serious case of the disease. Salk favored a simpler killed-virus polio vaccine intended to produce antibodies (through injection) without creating a natural infection. Speed was on Salk’s side in the race.

Human testing in the 1950s was, by current standards, a primitive affair. There were few rules or restrictions; researchers commonly used prisons and orphanages for their experiments without bothering with the modern-day niceties of “informed consent.” But the Salk trials, using a model in which some subjects would be given the real vaccine and others a placebo, required so many schoolchildren, in so many different regions of the country, that parental consent became an essential part of the process. No one could be certain that the Salk vaccine was safe or effective for humans; yet the parents of America volunteered their children in unprecedented numbers. Why? For one thing, many of them knew the March of Dimes, having worked as volunteers. For another, these parents had faced the terror of polio each summer for more than a decade. In their eyes, the risk of the vaccine paled in comparison to the promised reward. Finally, Americans of this era had an abiding faith in the power of scientific progress, especially medical research, which had discovered miraculous vaccines and wonder drugs against such scourges as pneumonia, tuberculosis, and yellow fever.

It took a full year to analyze the results of the polio trials. On April 12, 1955—the tenth anniversary of FDR’s death—the announcement was made: Salk had done it. His vaccine was “safe, potent, and effective.” Most heard the news huddled around their radios. In factories, department stores, and coffee shops, people wept openly with relief. To many, April 12 resembled another V-J Day—the end of a war. “We were safe again,” a journalist recalled. “We had conquered polio.” The following week, at a White House Rose Garden ceremony for Salk, President Dwight D. Eisenhower fought back tears as he told the young researcher: “I have no words to thank you. I am very, very happy.”

Sabin’s oral version appeared a few years later. Together, the two vaccines would end polio in United States and much of the world. The current expectation is that polio will soon go the way of smallpox, becoming only the second infectious disease to be wiped from the face of the earth. Most people today have no memory of polio—the images of deserted movie theaters and swimming pools, the panicked feelings of parents, the daily counts of polio victims in the newspapers, the common sight of toddlers struggling in their braces, the haunting photos of hospital wards lined wall-to-wall with iron lungs. It was a time of terror and of triumph, when Americans came together in a massive voluntary effort to defeat the twentieth century’s most insidious childhood disease.